   silently dropped.
 
   Events without times accrue in the current window."
-  [n & children]
+  [n start-time-fn & children]
   ; This is not a particularly inspired or clear implementation. :-(
 
   (when (zero? n)

                        ; No start time
                        (nil? @start-time)
                        (do
                          (ref-set start-time (:time event))
                          (ref-set buffer [event])
                          nil)


        (when events
          (call-rescue events children))))))

(defn- fixed-time-window-fn
  "A fixed window over the event stream in time. Emits vectors of events, such
  that each vector has events from a distinct n-second interval. Windows do
  *not* overlap; each event appears at most once in the output stream. Once an
